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From: Dmitry Osipenko <digetx@gmail.com>
To: Nicolin Chen <nicoleotsuka@gmail.com>,
	thierry.reding@gmail.com, joro@8bytes.org
Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	jonathanh@nvidia.com, hch@infradead.org,
	linux-tegra@vger.kernel.org
Subject: Re: [PATCH v4 1/2] iommu/tegra-smmu: Unwrap tegra_smmu_group_get
Date: Sat, 3 Oct 2020 17:27:56 +0300	[thread overview]
Message-ID: <0cc12c08-e2f2-b915-e7b4-8e2e94ea2ac4@gmail.com> (raw)
In-Reply-To: <35d789ae-7deb-7f8c-0556-98fe73f5999f@gmail.com>

29.09.2020 20:41, Dmitry Osipenko пишет:
> 29.09.2020 09:13, Nicolin Chen пишет:
>> The tegra_smmu_group_get was added to group devices in different
>> SWGROUPs and it'd return a NULL group pointer upon a mismatch at
>> tegra_smmu_find_group(), so for most of clients/devices, it very
>> likely would mismatch and need a fallback generic_device_group().
>>
>> But now tegra_smmu_group_get handles devices in same SWGROUP too,
>> which means that it would allocate a group for every new SWGROUP
>> or would directly return an existing one upon matching a SWGROUP,
>> i.e. any device will go through this function.
>>
>> So possibility of having a NULL group pointer in device_group()
>> is upon failure of either devm_kzalloc() or iommu_group_alloc().
>> In either case, calling generic_device_group() no longer makes a
>> sense. Especially for devm_kzalloc() failing case, it'd cause a
>> problem if it fails at devm_kzalloc() yet succeeds at a fallback
>> generic_device_group(), because it does not create a group->list
>> for other devices to match.
>>
>> This patch simply unwraps the function to clean it up.
>>
>> Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
>> ---
> 
> Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
> 

Tested-by: Dmitry Osipenko <digetx@gmail.com>
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WARNING: multiple messages have this Message-ID (diff)
From: Dmitry Osipenko <digetx@gmail.com>
To: Nicolin Chen <nicoleotsuka@gmail.com>,
	thierry.reding@gmail.com, joro@8bytes.org
Cc: vdumpa@nvidia.com, jonathanh@nvidia.com,
	linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org, hch@infradead.org
Subject: Re: [PATCH v4 1/2] iommu/tegra-smmu: Unwrap tegra_smmu_group_get
Date: Sat, 3 Oct 2020 17:27:56 +0300	[thread overview]
Message-ID: <0cc12c08-e2f2-b915-e7b4-8e2e94ea2ac4@gmail.com> (raw)
In-Reply-To: <35d789ae-7deb-7f8c-0556-98fe73f5999f@gmail.com>

29.09.2020 20:41, Dmitry Osipenko пишет:
> 29.09.2020 09:13, Nicolin Chen пишет:
>> The tegra_smmu_group_get was added to group devices in different
>> SWGROUPs and it'd return a NULL group pointer upon a mismatch at
>> tegra_smmu_find_group(), so for most of clients/devices, it very
>> likely would mismatch and need a fallback generic_device_group().
>>
>> But now tegra_smmu_group_get handles devices in same SWGROUP too,
>> which means that it would allocate a group for every new SWGROUP
>> or would directly return an existing one upon matching a SWGROUP,
>> i.e. any device will go through this function.
>>
>> So possibility of having a NULL group pointer in device_group()
>> is upon failure of either devm_kzalloc() or iommu_group_alloc().
>> In either case, calling generic_device_group() no longer makes a
>> sense. Especially for devm_kzalloc() failing case, it'd cause a
>> problem if it fails at devm_kzalloc() yet succeeds at a fallback
>> generic_device_group(), because it does not create a group->list
>> for other devices to match.
>>
>> This patch simply unwraps the function to clean it up.
>>
>> Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
>> ---
> 
> Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
> 

Tested-by: Dmitry Osipenko <digetx@gmail.com>

  reply	other threads:[~2020-10-03 14:28 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-29  6:13 [PATCH v4 0/2] iommu/tegra-smmu: Two followup changes Nicolin Chen
2020-09-29  6:13 ` Nicolin Chen
2020-09-29  6:13 ` [PATCH v4 1/2] iommu/tegra-smmu: Unwrap tegra_smmu_group_get Nicolin Chen
2020-09-29  6:13   ` Nicolin Chen
2020-09-29 17:41   ` Dmitry Osipenko
2020-09-29 17:41     ` Dmitry Osipenko
2020-10-03 14:27     ` Dmitry Osipenko [this message]
2020-10-03 14:27       ` Dmitry Osipenko
2020-10-08  9:55   ` Thierry Reding
2020-10-08  9:55     ` Thierry Reding
2020-09-29  6:13 ` [PATCH v4 2/2] iommu/tegra-smmu: Expand mutex protection range Nicolin Chen
2020-09-29  6:13   ` Nicolin Chen
2020-09-29 17:42   ` Dmitry Osipenko
2020-09-29 17:42     ` Dmitry Osipenko
2020-09-30  0:31     ` Nicolin Chen
2020-09-30  0:31       ` Nicolin Chen
2020-10-03 14:28     ` Dmitry Osipenko
2020-10-03 14:28       ` Dmitry Osipenko
2020-10-08  9:56   ` Thierry Reding
2020-10-08  9:56     ` Thierry Reding
2020-11-07  8:35 ` [PATCH v4 0/2] iommu/tegra-smmu: Two followup changes Nicolin Chen
2020-11-07  8:35   ` Nicolin Chen

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